KNbO3-BaTiO3 Piezoelectric Ceramic for Wide Temperature Range
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Solution Overview
Problem
Lead-based piezoelectric ceramics, such as PZT, pose environmental concerns due to lead elution, and lead-free alternatives like barium titanate (BaTiO3) have limited temperature range and low piezoelectric characteristics, necessitating a material with reduced lead content and improved performance across a wide temperature range.
Innovation Solution
A two-component solid solution of KNbO3 and BaTiO3 with a molar ratio of 0.5-0.9, which was previously believed to be non-piezoelectric, exhibits excellent piezoelectric characteristics and is environmentally friendly, with a relative density of 95% or greater, allowing for enhanced performance in a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric ceramics (PZT) are used, then excellent piezoelectric characteristics are achieved, but environmental harm increases due to lead elution
Solution Approach 1:
The invention extracts and removes the harmful lead component from the piezoelectric ceramic composition entirely, replacing it with a lead-free system comprising barium titanate and potassium niobate. This extraction eliminates the environmental harm from lead elution while maintaining piezoelectric functionality through the alternative material composition.
Solution Approach 2:
The invention employs a composite material system consisting of barium titanate (BaTiO3) and potassium niobate (KNbO3) in a specific compositional ratio. This composite lead-free material combines the advantages of both components to achieve satisfactory piezoelectric characteristics without the environmental drawbacks of lead-based ceramics.
2Object-affected harmful factors
If barium titanate is used as a lead-free alternative, then lead content is reduced, but the usable temperature range is limited to no higher than 100°C
Solution Approach 1:
The invention changes the compositional parameters of the barium titanate-based system by introducing potassium niobate in a specific ratio range (0.05-0.30 mol fraction of KNbO3). This parameter modification raises the Curie temperature from 120°C to above 300°C, thereby expanding the usable temperature range while maintaining the lead-free advantage.
Solution Approach 2:
The invention creates a composite material system combining barium titanate and potassium niobate, where the interaction between the two components modifies the thermal properties of barium titanate. The composite structure enables the material to operate at higher temperatures than pure barium titanate while remaining lead-free.
3Object-affected harmful factors
If barium titanate-based lead-free ceramics are used, then environmental friendliness is improved, but piezoelectric characteristics and generated displacement are insufficient
Solution Approach 1:
The invention optimizes the compositional parameters by precisely controlling the potassium niobate content within the range of 0.05-0.30 mol fraction. This parameter optimization enhances the piezoelectric characteristics and generated displacement to levels comparable with or exceeding conventional lead-based ceramics, while maintaining environmental friendliness through the lead-free composition.
Solution Approach 2:
The invention exploits phase transition phenomena in the barium titanate-potassium niobate system, utilizing the phase boundary between tetragonal and orthorhombic crystal structures. By positioning the composition near this phase boundary, the material exhibits enhanced piezoelectric characteristics due to the increased polarizability associated with the phase transition behavior.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The KNbO3-BaTiO3 solid solution provides satisfactory piezoelectric characteristics and reduced lead content, making it suitable for various applications while maintaining high performance across a broad temperature range, addressing the limitations of existing lead-free materials.
Implementation Method 1
Known piezoelectric ceramics exhibit piezoelectricity, whereby application of an electric field generates mechanical strain and stress
Data Source
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AI summary
The piezoelectric element (20) of the invention comprises a pair of electrodes (2,3) and a piezoelectric ceramic (1) comprising as the major component a solid solution of the two components KNbO3 and BaTiO3. In the solid solution, the molar ratio of KNbO3 is 0.5-0.9 with respect to the total of the two components.